"Local Measurement of the Superfluid Density in the Pnictide Superconductor Ba(Fe1-xCox)2As2 across the Superconducting Dome"

Lan Luan: Thomas M. Lippman, Clifford W. Hicks, Julie A. Bert, Ophir M. Auslaender, Jiun-Haw Chu, James G. Analytis, Ian R. Fisher, and Kathryn A. Moler; Phys. Rev. Lett., 02/09/11.

Additional Authors: Thomas M. Lippman, Clifford W. Hicks, Julie A. Bert, Ophir M. Auslaender, Jiun-Haw Chu, James G. Analytis, Ian R. Fisher, and Kathryn A. Moler

Abstract:

We measure the penetration depth λab(T) in Ba(Fe1-xCox)2As2 using local techniques that do not average over the sample. The superfluid density ρs(T)≡1/λab(T)2 has three main features. First, ρs(T=0) falls sharply on the underdoped side of the dome. Second, λab(T) is flat at low T at optimal doping, indicating fully gapped superconductivity, but varies more strongly in underdoped and overdoped samples, consistent with either a power law or a small second gap. Third, ρs(T) varies steeply near Tc for optimal and underdoping. These observations are consistent with an interplay between magnetic and superconducting phases.